However, you should be able to use a regular camera in waterproof housing, with a white semi-opaque bulb covering the port. Calibrate ISO/shutter/aperture on the surface to a standard light meter reading, and then take measurements with the camera's exposure meter underwater. Match the underwater exposures to your calibrated measurements to determine your ambient light (note, there may be some shift for meter WB correction).

Steve could be right, though, if they're trying to figure out how much more light is required to sustain photosynthetic life at depths.

These multiple entries are correct and do not need to be deleted from your list.

The entries above are all for the same species, a Gymnothroax equatorialis. If you notice, each entry starts with a different common name of the same animal. Lightroom only "sees" the first word in a line of keywords when autofilling in the Enter Keywords box. Therefore Lightroom would not autofill the "add keyword tag line" if the species keyword was only in our list starting with spot tail moray and the user typed spotted-tail moray. You would then feel our list is incomplete.

I believe this issue is avoided if one uses the "Filter Keywords" search option (Alex's method #2) under Keyword List. In the same way that keyword entries are not duplicated to put Latin species names first, it's probably cleaner to have single entries rather than triplicate for multiple common names.